Hi Mukesh, On Fri, 31 Jul 2026 15:34:21 -0700 Mukesh R <[email protected]> wrote:
> Add a new file to implement basic VFIO-MSHV bridge pseudo device. > These functions are called in the VFIO framework, and credits to > kvm/vfio.c as this file was adapted from it. This is a basic version > to build upon. > > Co-developed-by: Wei Liu <[email protected]> > Signed-off-by: Wei Liu <[email protected]> > Signed-off-by: Mukesh R <[email protected]> > --- > drivers/hv/Makefile | 3 +- > drivers/hv/mshv_vfio.c | 211 > ++++++++++++++++++++++++++++++++++++++ include/uapi/linux/mshv.h | > 1 + 3 files changed, 214 insertions(+), 1 deletion(-) > create mode 100644 drivers/hv/mshv_vfio.c > > diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile > index 888a748cc7cb..9ab6fc254c38 100644 > --- a/drivers/hv/Makefile > +++ b/drivers/hv/Makefile > @@ -14,7 +14,8 @@ hv_vmbus-y := vmbus_drv.o \ > hv_vmbus-$(CONFIG_HYPERV_TESTING) += hv_debugfs.o > hv_utils-y := hv_util.o hv_kvp.o hv_snapshot.o hv_utils_transport.o > mshv_root-y := mshv_root_main.o mshv_synic.o mshv_eventfd.o > mshv_irq.o \ > - mshv_root_hv_call.o mshv_portid_table.o mshv_regions.o > + mshv_root_hv_call.o mshv_portid_table.o > mshv_regions.o \ > + mshv_vfio.o > mshv_root-$(CONFIG_DEBUG_FS) += mshv_debugfs.o > mshv_root-$(CONFIG_TRACEPOINTS) += mshv_trace.o > mshv_vtl-y := mshv_vtl_main.o > diff --git a/drivers/hv/mshv_vfio.c b/drivers/hv/mshv_vfio.c > new file mode 100644 > index 000000000000..92cfbaef0328 > --- /dev/null > +++ b/drivers/hv/mshv_vfio.c > @@ -0,0 +1,211 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * VFIO-MSHV bridge pseudo device > + * > + * Heavily inspired by the VFIO-KVM bridge pseudo device. > + */ > +#include <linux/errno.h> > +#include <linux/file.h> > +#include <linux/list.h> > +#include <linux/module.h> > +#include <linux/mutex.h> > +#include <linux/slab.h> > +#include <linux/vfio.h> > +#include <asm/mshyperv.h> > + > +#include "mshv.h" > +#include "mshv_root.h" > + > +struct mshv_vfio_file { > + struct list_head node; > + struct file *file; /* list of struct mshv_vfio_file */ > +}; > + > +struct mshv_vfio { > + struct list_head file_list; > + struct mutex lock; > +}; > + > +static bool mshv_vfio_file_is_valid(struct file *file) > +{ > + bool (*fn)(struct file *file); > + bool ret; > + > + fn = symbol_get(vfio_file_is_valid); > + if (!fn) > + return false; > + > + ret = fn(file); > + > + symbol_put(vfio_file_is_valid); > + > + return ret; > +} > + > +static long mshv_vfio_file_add(struct mshv_device *mshvdev, unsigned > int fd) +{ > + struct mshv_vfio *mshv_vfio = mshvdev->device_private; > + struct mshv_vfio_file *mvf; > + struct file *filp; > + long ret = 0; > + > + filp = fget(fd); > + if (!filp) > + return -EBADF; > + > + /* Ensure the FD is a vfio FD. */ > + if (!mshv_vfio_file_is_valid(filp)) { > + ret = -EINVAL; > + goto out_fput; > + } > + > + mutex_lock(&mshv_vfio->lock); > + > + list_for_each_entry(mvf, &mshv_vfio->file_list, node) { > + if (mvf->file == filp) { > + ret = -EEXIST; > + goto out_unlock; > + } > + } > + > + mvf = kzalloc(sizeof(*mvf), GFP_KERNEL_ACCOUNT); > + if (!mvf) { > + ret = -ENOMEM; > + goto out_unlock; > + } > + > + mvf->file = get_file(filp); > + list_add_tail(&mvf->node, &mshv_vfio->file_list); > + Why there is no vfio_device_file_set_kvm equivalent for mshv? since VFIO device open/bind path will do vfio_device/group_get_kvm_safe() to ensure lifetime alignment. Otherwise, vfio group/device can outlive mshv partition. If we do want to support this kvm-vfio bridge semantics beyond kvm, maybe this should be abstracted as a generic VFIO "hypervisor partition" association, with hypervisor-specific get/put callbacks, rather than adding an MSHV-only copy of the KVM hook. +Alex > +out_unlock: > + mutex_unlock(&mshv_vfio->lock); > +out_fput: > + fput(filp); > + return ret; > +} > + > +static long mshv_vfio_file_del(struct mshv_device *mshvdev, unsigned > int fd) +{ > + struct mshv_vfio *mshv_vfio = mshvdev->device_private; > + struct mshv_vfio_file *mvf; > + long ret; > + > + CLASS(fd, f)(fd); > + > + if (fd_empty(f)) > + return -EBADF; > + > + ret = -ENOENT; > + mutex_lock(&mshv_vfio->lock); > + > + list_for_each_entry(mvf, &mshv_vfio->file_list, node) { > + if (mvf->file != fd_file(f)) > + continue; > + > + list_del(&mvf->node); > + fput(mvf->file); > + kfree(mvf); > + ret = 0; > + break; > + } > + > + mutex_unlock(&mshv_vfio->lock); > + return ret; > +} > + > +static long mshv_vfio_set_file(struct mshv_device *mshvdev, long > attr, > + void __user *arg) > +{ > + int32_t __user *argp = arg; > + int32_t fd; > + > + switch (attr) { > + case MSHV_DEV_VFIO_FILE_ADD: > + if (get_user(fd, argp)) > + return -EFAULT; > + return mshv_vfio_file_add(mshvdev, fd); > + > + case MSHV_DEV_VFIO_FILE_DEL: > + if (get_user(fd, argp)) > + return -EFAULT; > + return mshv_vfio_file_del(mshvdev, fd); > + } > + > + return -ENXIO; > +} > + > +static long mshv_vfio_set_attr(struct mshv_device *mshvdev, > + struct mshv_device_attr *attr) > +{ > + switch (attr->group) { > + case MSHV_DEV_VFIO_FILE: > + return mshv_vfio_set_file(mshvdev, attr->attr, > + > u64_to_user_ptr(attr->addr)); > + } > + > + return -ENXIO; > +} > + > +static long mshv_vfio_has_attr(struct mshv_device *mshvdev, > + struct mshv_device_attr *attr) > +{ > + switch (attr->group) { > + case MSHV_DEV_VFIO_FILE: > + switch (attr->attr) { > + case MSHV_DEV_VFIO_FILE_ADD: > + case MSHV_DEV_VFIO_FILE_DEL: > + return 0; > + } > + > + break; > + } > + > + return -ENXIO; > +} > + > +static long mshv_vfio_create_device(struct mshv_device *mshvdev) > +{ > + struct mshv_device *tmp; > + struct mshv_vfio *mshv_vfio; > + > + /* Only one VFIO "device" per VM */ > + hlist_for_each_entry(tmp, &mshvdev->device_pt->pt_devices, > + device_ptnode) > + if (tmp->device_ops == &mshv_vfio_device_ops) > + return -EBUSY; > + > + mshv_vfio = kzalloc_obj(*mshv_vfio); > + if (mshv_vfio == NULL) > + return -ENOMEM; > + > + INIT_LIST_HEAD(&mshv_vfio->file_list); > + mutex_init(&mshv_vfio->lock); > + > + mshvdev->device_private = mshv_vfio; > + > + return 0; > +} > + > +/* This is called from mshv_device_fop_release() */ > +static void mshv_vfio_release_device(struct mshv_device *mshvdev) > +{ > + struct mshv_vfio *mv = mshvdev->device_private; > + struct mshv_vfio_file *mvf, *tmp; > + > + list_for_each_entry_safe(mvf, tmp, &mv->file_list, node) { > + fput(mvf->file); > + list_del(&mvf->node); > + kfree(mvf); > + } > + > + kfree(mv); > + kfree(mshvdev); > +} > + > +const struct mshv_device_ops mshv_vfio_device_ops = { > + .device_name = "mshv-vfio", > + .device_create = mshv_vfio_create_device, > + .device_release = mshv_vfio_release_device, > + .device_set_attr = mshv_vfio_set_attr, > + .device_has_attr = mshv_vfio_has_attr, > +}; > diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h > index be6fe3ee8707..b038a79786d2 100644 > --- a/include/uapi/linux/mshv.h > +++ b/include/uapi/linux/mshv.h > @@ -254,6 +254,7 @@ struct mshv_root_hvcall { > #define MSHV_GET_GPAP_ACCESS_BITMAP _IOWR(MSHV_IOCTL, 0x06, > struct mshv_gpap_access_bitmap) /* Generic hypercall */ > #define MSHV_ROOT_HVCALL _IOWR(MSHV_IOCTL, 0x07, > struct mshv_root_hvcall) +#define MSHV_CREATE_DEVICE > _IOWR(MSHV_IOCTL, 0x08, struct mshv_create_device) > /* > ********************************
